More than 500 people joined a protest against plans for a rubbish incinerator in Newhaven.
Dozens of campaigners met at Paradise Park at 9am today for the walk to the public inquiry examining the burner plans.
More than 100 walked the full distance to Lewes to listen as toxicologist Dr Vyvyan Howard outlined the health risks of incineration.
Dozens more caught the train and filled the inquiry room with placards and banners.
They listened as Dr Howard said incineration was "not safe".
More than 450 walkers and protesters had signed the inquiry register by noon, sometimes forming long queues, with more people still arriving.
Walk organiser Alfred Medhurst said: "To get so many people to turn up on a Tuesday morning was fantastic. It was just brilliant."
Barbara White walked from Newhaven to Southease and then caught the train on to Lewes.
She said: "We feel very strongly that we don't want this incinerator in Newhaven. We just feel that it will cause health problems for us."
Fellow walker Doris Winton, said: "I am annoyed about this idea of having this terrible thing put upon us. It is wrong."
Eve Taylor, who walked the whole seven-and-a-half-mile route, said: "I don't want the incinerator because I do think it will be exceedingly hazardous to all of us.
"I think everything will be polluted, the ground, the water, everything. The walk was wonderful, it was worth it."
The inquiry, which ends this week, is examining waste plans drawn up by the Brighton and Hove City Council and East Sussex County Council, for an incinerator at North Quay, Newhaven.
The inspector's report is not expected to be made public until the middle of next year.
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